Tie line for automatic telephone exchanges



TIE LINE FOR AUTOMATIC TELEPHONE EXCHANGES Original Filed May 14, 1945 G. DEAKIN Margh 29, 194 9.

4 Sheets-Sheet l JUNCTION DIAGRAM TIE LINE INVENTOR. G ERALD DEAKI N J f l I STARTING CIRCUIT AGENT March 29, 1949. G. DEAKIN TIE LINE FOR AUTOMATIC TELEPHONE EX Original Filed May 14, 1945 CHANGES 4 Sheets-Sheet 2 March 29, 1949.- G. DEAKIN 2,465,359

TIE LINE FOR AUTOMATIC TELEPHONE EXCHANGES Original Filed May.l4, 1945 4 Sheets-Sheet 3 nrU'H a G0 LU 9* J g; H as lHll- U2 n 7 x \F 2 or 3 A 3 H 5 L2 F v INVENTOR. D GERALD DEAKIN GEN G. DEAKlN 2,465,359

TIE LINE FOR AUTOMATIC TELEPHONE EXCHANGES March 29, 1949.

4 Sheets-Sheet 4 Original Filed May 14, 1945 m K mm. m M M q. m .A m E G, Y B .r o U m Patented Mar. 29, 1949 t 2,465,359 TIE LINE FOR AUTOMATIC TELEPHONE EXCHANGES Gerald Deakin, New York, N. Y., assignor to International Standard Electric Corporation, New York, N. Y., a corporation of Delaware Original application M"... 14, 1945, Serial No.

1945, Serial No. 594,873

9 Claims. (Cl. 17918) This invention relates to new and useful improvements in multi-exchange telephone switching systems.

The present is a division of my application, Serial No. 593,602, filed May 14, 1945.

The object of the present invention is to provide for switching over a two-wire, two-way tie line between two automatic telephone exchanges, such as two private automatic branch exchanges.

Throughout the specification the term B link is used to denote a trunk comprising a set of relays by means of which a line finder is connected with a first group selector and may also be connected with a register.

Also throughout the specification the term R link has been used to denote a circuit comprising a set of relays which may be connected by means of finder switches with the B link and also with the register.

The various features of the invention will more clearly appear from the following description of an embodiment with reference to the drawings, in which:

Fig. 1 is a junction diagram of two P. A. B. X's

. inter-connected by. a tie line forming the object of the present invention;

Fig. 2 shows the important portions of a :substation at a P. A. B. X and a line finder through which the substation may be extended;

Fig. 3 is a local link at the P. A. B. X connected with the line finder of Fig. 2 and having at its other end a group selector;

Fig. 4'illustrates an R-link which may connect a register also diagrammatically shown in this figure with a local link of Fig. 3; and

Fig. 5 illustrates the terminal equipment of'the tie line.

Divided and this application May 21,

ter A is converted to dial pulsing as on anouttrunk call. These pulses are received by the tie line at P. A. B. X B and converted by the tie line to normal key pulses so as to operate register B in the normal way. The tie line at the receiving end acts as a repeater-translator.

Stationkeys tie line digit 7 B-link: at P. A. B. X A chooses idle tie line The group selector (Fig. 3) of the selected B- link hunts for a free tie line (Fig. 5) the T-terminal of which has potential PN1 applied over ER,

"1BR, KR, FR back. When a free tie line is found,

theregister (Fig. 4) stops the group selector and .makes ,the customary second test.

Only the circuits of the tie line terminal equipv ment are shown in detail; all the others have been which are served by the line. The method of operation is the same no matter at which end of the tie line the call originates. Each end isconnected to the banks of the line finders and group selectors of local B-links at the two P. A. B. X's. At P. A. B. X A, the group selector of a B-link picks up one end of the tie line at a P. A. B. X "B," the line finder of a local B-link picks up the other end of the tie line. A register is connected with the local B-link at each P. A. B. X through an R-link in the usual way.

It is assumed that thetie line number is 7 Wheneverthis digit is keyed by a station I, regis- Register A converted to out-trunking 1 When RCR (Fig. 4) makes its front contact, it closes a circuit from ground, brush E of the outcontrol switch terminal I, front RCR, winding low resistance DRR, front XR2, front XR3, back XRI, back RHR, windingRHR to battery. RHR operates and locks up over a front contact of RIR. As soon as RHR breaks its back contact, DRR releases and RCR short-circuits XR2 and XR3. These relays release and in turn release XHRI. RHR energizes RMR (Fig. 4) which disconnects brushes F and G from the normal selection circuit and in place thereof connects them to the outtrunk dial pulsing circuit.

When RCR releases, P0 goes from position I to position 2.

P. A. B. X A end of tie line operates When the group selector reaches the tieline, the first test over the t wire may be traced from terminal T (Fig. 5) ,back FR, back KR, back BR, back ER, resistor to potential PN1. The second test over the b wire may be traced from the B-terminal, back JR, back BR,"second back BR, back ER, resistor to potential'PNl.

After thesecond test, AR (Fig. 5) operates, circuit from ground (Fig. 3), front RR, back FR2, winding low resistance CR2, lower contact ,ONCZ, low resistance winding of BR,.front BR, back AR, brush C, back KR, (Fig.5), back BR, back FR,

to the C-terininaL BR disconnects'the B-terminal from the T-terminal, disconnects the bridge, including relay CR, from the tie line: When AR releases and removes ringing current from the tie line, the a and 12 wires are'extended through from the A and B terminals of; the group selectors to the distant P. A. B?

"3 end of tie Zine operates In tracing the following circuits, one must bearin mind that the B exchange end of the tie line is a mirror image of the A end shown in Fig. 5,

When relay AR (Fig. 5) applies ringing current v to the. called end, relay, CR of the tie line in P; A. B. X .Bfbnerates' 'inseries with condenser C3] and locks up over adircriit from ground, back FR, front CR, winding CR, winding'ER to battery." CR also,'energiz'"efsf slow. release relay n a' s'a h ld n hun ss t A and B bank terminals. 'This'circ'uit may be traced from terminal A, back JR, back HR, resistor R, front RiA, baclsI-IR, back JR to the B-terminal. This will hold the register when one is connected to the tie line, as explained hereinafter.

- "RJR, (Fig; 5) also energizles 132a and magnet P of a marker switch hayingbrushes A and B, The brushes do notadyance' from position 1 to position 2 until the circuit of P is opened by DR when the latter operates. Contacts X and 'Y of the mar et w ieh 9 0$: a f m s 0 i its home position 1.

R-link, J s-Link and tiyister. connected, to tie li e "eetexe+ When ER in P. A. B. I; "13 operates, it energizes'the 'start'in'g, circuit (Fig. 2) f andplacesfp'otential PC on are" t" wire, circuit from PC (Fig'. 5), resistor, front ER, bag BR, fiQ KR, back PR to the T-terr'nirfal. All R-Iiiik at the P. .A. B. XfBflipicksupa B-link and then a register, after which the register. causes the line finder of the B-link to pickup the tie. line. exactly as. though a station in P. A. B. X B3? were. calling. The tie line. is double tested'in the usual way. When the linefinder at the B-exchangev seizes the tie. line, m. operates. Thecircuit from the C-terminalat the Bend on the tie.:line maybe traced overqback KR, back. BR, back. front ER, winding. FR to, battery. FR. locks, up to thef-c? wire "and bridgespulsing relay. DRv across the "a andfb. wires. DR operatesinseries. with PR (Fig. 4) of the register and the marker. switch goes. from position 1 toposition 2 when 1?; de-energizes.

The opening circuit of DR (Fig. 5) at. A. B.-X B may be traced from ground, one winding of DR, frontFR, b wire tar. A. B. X A, back FR, front BR, back JR, terminal A, brushA of group selector'(Fig. 3 thence through the B,-li nl a k ieo q m na o e iste t exchange A, front RMR, winding PR, and iri'parlallel rectifier Si, back RKR, back RUR. front RMR, terminalF; than a'na Blinks (Fig; s) v to brush B of thegroupselector, thence terminal B of, the. tie line (Fig.6) back JR," r o itBR. back AR, bacl; FR'flfaf Wire to] P. AB, X B,- front FRandtheother winding'of DR tobattery, The direction ofourrent flowis ,suchv as to operatePR w mergin o trunk" call.

. "*YfTo'f P, brush A, ter

Station 1 keys number of station 2 The subscriber at station 1 (Fig. 2) keys Il'cllli her 635 which we will assume is the number of 5 station 2, and the digits 6, 3 and 5 are recorded are tandby he nd. th s and fir groups of digit-storing relays, respectively, of the register at P. A. B. X A in the same manner as the first three digits of a city number on an out- Reqister A transmits dial pulses to tie line at RARXW" When PR (Fig. 4) of the register operates, it energizes PAR which locks up over a front contact of R |R, PAR connects PR! in series with rectifier S2 in multiple with PR and SI but as 3 has the opposite polarity of Si, no current dwsthrough PRI until pulsing is completed, as

er la es ter- 3B i c a s-sine c rcu t of and 2? dial p ls corre po d n to. th first digit 6 are sent out by RKR exactly as on cit sa t Th metk rsw teh P (F s-v (I the tie 'lineat P. A; B. X B, advances six steps; that i qx nositiel gq it a Conversion of dial-type pulses tolqeihtype pulses Brushes A and B of the step-by-step switch P 30 atRA. B. X"B," as previously stated, are in position 2 when pulsing starts. They may be advanced one to ten steps dependingupon the number of pulses sent'by the register A. RZR. doesnot fall off during pulsingbutat the end of a series of 3 pulses DR remains on its front contact long enough to allow RZRto make its back contact and to release R3R.

When one pulse is sent by-register A, DR at the B exchange advances P to position 3. When R ZR i imakes itsback contact, it energizes HR over contact Y,"brush'-A"and terminal 3'. HR is a long changeover relay. and" when. it breaks its back contacts it releases ARI (Fig. 4) of theregister at B; When. it makesitsfrontcontacts, it bridges 4 :resistorlRl; (Fig. 5) across the. a and b "wire's leading to register B, and. also-rectifier S in series with resistor R. Therectifler is sopolarized that the. circuit simulates. the condition when key l (Fig. 1 is depressed.

'When brlush' Biof the marker switch. is. advanced twosteps to terminal 4, it simulates the condition that exists when key. 2 isdepressed, and so on. When brushes/A and. Bare advanced six-steps, corresponding to theLdigitIG, resistor-RI isbridged 55 across the registerrdircuitand at thesame'time the connections ofazectifler- S are. reversed by: GR, thus simulating the depression of key 6 at a'calliing. station.

Q0 Register B receives key-type pulses fromitie line IE. 99. I'QQQYWSJQBI first. Settl s. of l es. sends; P: Bas ien harf R23, re e ses. i ses av irc itrem-e eima. ack. RIB; contact 1t mcimagawmd;

es- 33.1 attery. 4 ent re x lained he tens eenq tisn Qf:1 8 simulated r get s e l st adines :d ts; are: hic sen s he. mergencies r. he .Br lli'mfi- A, B.-

10 X. 3? w. ssia fina de tities! y. t tia ,m, nanreleasas hp t rei sr R.2.. an1; 1 turn t h m 99 1 93 The remaining two. digits l 3, 8.9 1 5. arereceived b -hef tie e ret A- 3.1 r i? miiausua w s Belink (Fig. 3), 1'5 wiraback AR.- of linezfinden (Fig. 3),, brush T, ('the t wire circuitvia the group selector: is. open: at. the. final)*,, terminal '12 of; tie-line (Fig. 59 front. FR, one winding; of KB. in ground. does not at. this. moment: operate because of the presence of resistor R. However; when theselectionlofthe called line is completed, register B releases and sends the R-link to the ringing or busy position, as the case may be. Full battery is now placed: on the d wire of the R-link (Fig. 3) or the t wireof-,the tiei line (Fig. over either interrupter Fl.l or;Fl2.. This full battery operates KR (Fig. 5)" which looks up to the c wire over a second. winding, at thesame time releasing, ER, and energizing BR. JR? does not operateas it doesat the originating P'..A'. B. X A. sincev KR, has. opened. its. operating circuit;

A momentary holding circuit is now established from the bridge in register A to the bridges relays GRI (Fig. 4) and GR2 in the R-link at P. A. B. X B.

Register A and R-lz'nk at P. A. B. X A release During pulsing the direction of current fiow in the a and b wires from DR (Fig. 5) at P. A. B. X B to P. A. B. X A is such as to operate relay PR (Fig. 4) of register A. However, when FR (Fig. 5) is released, the direction of current flow in the a and b wires is reversed and current now flows from the G-terminal (Fig. 4) of register A to the F-terminal and consequently over front PAR, winding PR! and rectifier S2. PRI operates RUR. which releases the register as on an out-trunk call.

Holding shunt placed on tie line at P. A. B. X A

RUR places full battery on the d" wire of the R-link which is transmitted through the R and B links and group selector to the t wire of the tie line (Fig. 5) and energizes JR, which relay did not operate when XHR3 (Fig. 4) placed battery on the 11 wire through resistor R. The circuit from the T-terminal may be traced back via back FR (Fig. 5), back KR, front BR, back AR, winding JR. to ground. JR locks up over a front contact and a front contact of BR, at the same time disconnecting itself from the t wire. JR removes the short-circuit from transmission condensers Cl and C2 and places the holding retardation coil shunt across the originating end of the tie line, thus holding the R-link and subsequently the B-link busy at P. A. B. X B. Condensers Cl and C2 prevent a flow of current from the transmission relays SIR and SZR in the B-link (Fig, 3) at P. A. B. X A. The tie line circuit is operated and maintained on a full metallic basis.

Called station 2 answers When the called station 2 answers, the R-llnk at P. A. B. X B releases in the usual manner and the tie line connection is established through the B-links at P. A. B. Xs A and B.

Release The release of the connection is always under the control of the originating station; that is, station I of P. A. B. X A. When this station hangs up, the B-link releases in the usual manner and freeszthe; tie*-1ine-,';whereupon:BR and JR (Eig.

release and. remove shunt from the tie line; Supervisoryrelay S IR of the B link. at .P. A. B. X B falls; away and. releases the connection at the distant 1?. A, B..X. What laclaimi-sr I. Inatelephone system, two exchanges;. a: line having. twolike ends: at. the exchanges interconnected by two wires, a plurality of stations, local links and. switching. means at each exchange, means. for operating said switching means to establish connections; between a. calling and a called: station at are exchange, or a calling or called station and; the end. of the line, a control relay' at each exchange normally" disconnected from: therline, means controlled by the calling exchange for connecting the relay at the called exchange with the two wires of the line, means controlled by the calling exchange fonconnecting the end oi? the lineatith'ecalled exchange with the switching means thereat, and means controlled by the connected relay for operating. the: lastm'entioned switching: means. I

2. The system according to claiml, a plurality of line finders at each exchange, each local link having the wipers of a finder at one and the wipers of a selector at the other end, terminal banks with which said wipers cooperate, and multiple connections from the two-wire portion of the line to the banks of the finders and selectors at both exchanges.

3. In a telephone system, two exchanges, a line having four-wire ends at the exchanges interconnected by two wires, a plurality of stations at each exchange, local links and. selectors at each exchange, means for operating said selectors to establish connections between a calling and called station at an ofiice or a calling station and the four-wire end of the line, a relay at each exchange normally disconnected from the line, means responsive to the selection of the line at a calling exchange for connecting with the two wires thereof the relay at the called exchange, means also responsive to said selection for connecting with the four-wire end of the line at the called exchange a local link, and means controlled by said relay at the called exchange for controlling the operation of the selectors thereat to select a called line.

4. In a telephone system a plurality of private automatic branch exchanges, tie lines interconnecting them, each having a two-wire portion and two four-wire'ends, the latter at two different exchanges, a plurality of stations at each exchange, line finder and selector switches at each exchange, local links connecting the wipers of said switches in pairs, terminal banks with which said wipers cooperate and with which the twowire portion of a tie line is connected in multiple at each exchange, means including a register at each exchange for operating said switches to establish connections between a calling and called station at an exchange or a callin station and the four-wire end of an idle tie line leading to the called exchange, a stepping relay at each exchange normally disconnected from the line, means responsive to the selection of a tie line at a calling exchange for connecting with the two wires thereof the stepping relay at the called exchange, means also responsive to said selection for connecting with the four-wire end of the selected tie line at the called exchange a local link and a register therewith. and means controlled by said stepping relay at the called exchange for operating the last-mentioned register.

5. In a telephone system, two exchanges, a two-way trunk interconnecting them, a plurality of stations at each exchange, a controller at each station operable in accordance with the digits of the called number, automatic switching means at each exchange for connecting a calling or called station with the trunk, numerical control equipment associated with the switching means at each exchange for controlling its operation as determined by the controller of the calling station, second numerical control equipment associated with the trunk at each exchange but normally disconnected therefrom, means for operating the second control equipment at the called ofllce as determined by the controller of the calling station, and means controlled by said second equipment for operating the control equipment of the switching means at the called ofilce.

6. The system according to claim 5, and in which the first-mentioned control equipment is a register.

7. The system according to claim 5, and in which the second control equipment is a stepby-step switch.

exchange.

GERALD DEAKIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,224,374 Goodrum May 1, 1917 2,289,895 Abbott July 14, 1942 2,380,950 Deakin Aug. 7, 1945 

